Radio signaling system



J. WEINBERGER RADIO SIGNALING SYSTEM 2 Sheets-Sheet 1 1 Filed Oct. 11. 1921 I 1,512,960 J. WEINBERGER RADIO IGNALING SYSTEM Filed Oct. 11. 1921 2 Sheets-Sheet 2 (D 2 I O z 30 A R-F-CURRENT ,9 INRMPERES f, 2.5 8 O Y E 2-0o i LSD-o V7 5 0-75 so m0 200 D13. AMPERE TURN6 amount duuu WEINBERGER @3913 hi/babbomu 2 MM Patented @ct. 28, I924.

'urren STATES PATENT OFFICE.

JULIUS WEINBERGER, OF NEW YORK, N. Y., ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE.

RADIO SIGNALING SYSTEM.

Application filed October 11, 1 921. SeriaiNc. 507,103.

To all whom it may concern:

Be it known that I, JULIUs WEINBERGER, a citizen of the United States, residing in the borough of Manhattan, city, county, and State of New York, have invented certain new and useful Improvements in Radio Signalin Systems, of which the following is a speci cation.

This invention relates to transmitting systems for radio signaling and particularly to a method of and an arrangement for controlling the amplitude of high frequency signaling currents. The invention is applicable to radio telegraphic or radio tele phone transmitters, but for purposes of illustration the invention will be particularly described with reference to radio telephonic modulation as it is particularly suitable for this purpose.

In accordance with one aspect of the invention the amplitude of the high frequency current is varied by means of an arrangement in which the variation of a low frequency magnetization circuit having an iron core cooperates with a high frequency winding on the core to greatly vary the effective resistance of the latter. The change in the resistance of the high frequency winding is due to the change of the iron losses of the core when the direct current magnetization is varied. With the former types of ferromagnetic modulator a change in induc tance occurs and this phenomenon has heretobefore been used to cause modulation of the radiated energy due to the detuning efiect. The present arrangement varies the inductance to some extent, but is utilized under conditions where the change of the iron losses is the controlling factor. This condition is most readily realized at high frequencies (300,000 cycles or more) at which frequency I have found that the resistance variation in its efiect on the antenna current is large compared with the inductance varia tion while with lowfrenquencies the reverse condition would normally tend to prevail. In order that the resistance variation may be efiective for modulating without appreciable modulation by inductance variation or detuning, the ratio of total inductance to the change of inductance should-"be hi h and the ratio of the total resistance to t e change of resistance should be low. These conditions occur is the arrangement device an a telephone connected with the antenna so as to vary the effective resistance 1 of the antenna. By this means a larger current can be modulated by. resistance changes than when an ordinary microphone in the antenna is used for this purpose. I have discovered that with the ferromagnetic modulator the resistance of the high frequency circuit may be varied by means of such small direct current variations as are obtainable with an ordinary microphone or telephone transmitter. I have further discovered that it is possible by proper selection of the turns of the high frequency and low frequency windings and the dimensions of the core to produce this variation of resistance at frequencies corresponding to relatively short wave lengths (1,000 meters or less) while producing only variations in the inductance of the high frequency winding which are inefi'ective for modulation or detuning. Modulation by resistance in the manner described is especially advantageous because the radiation of interfering frequencies is eliminated and the radiation is practically limited to the desired frenquency.

In the drawings:

Fig. 1 is a diagrammatic illustration of a radio telephone transmitter in accordance with the invention.

Fig. 2 is a set of curves illustrating the operating characteristics of the apparatus.

In Fig. 1 reference the antenna grounded at 2. A high frequency oscillation generator 3 is coupled to the antenna by means of a high frequency transformer having its primary coil 4 in the generator circuit and its secondary coil 5 in the antenna circuit. Although various t es of oscillation generators ma be utilized I have illustrated an espec' y simple and desirable form for an amateur radio telephone comprisingeone or more three-electrode vacuum tn 5 having the filament 6 connected to the plate 6 through a source of E. M. 'F. 7 shunted by a condenser 7 to by characterv 1 designates 1" pass radio frequencies. The primary coil 4 is connected between the generator and plate and a coil 8 connected to the grid and filament is coupled to the primary coil 4.

The controllin arrangement for varying the amplitude o the oscillations comprises a winding in the aerial wound on an iron core, a second winding n the core connected outside dimensions, with arms 1.4 cm. wide an ordinary microphone telephone transmitter 15.

The .use of the vacuum tube oscillator without a modulating means connected thereto enables the operation and'the circuits to be greatly simplified. Modulating tubes which complicate the circuits and increase the initial cost and upkeep are eliminated as well as numerous circuit elements which are required when modulating tubes are used. The change of resistance of the magnetic modulator is used to directly af-' feet the antenna current.

he twocores in the modulator circuit with'direct current windings in opposite directions are used to prevent the variations in the antenna current from inducing similar changes in the direct current windin Theinvention however is not necessarif limited thereto. JW I For purposes of illustration in Fig. 2 the operating characteristics of the system shown are illustrated with a hollow rectangu-' lar iron core. 4 cm. Wide and 5.3 cm. long and built up of 25 pieces of laminated sheet iron (.05.01 cm. thick). The direct current winding consists of 100 'turnson each core wound in opposite directions connected .to a

battery of six volts and a microphone. With a microphone through which .4 ampere flowsthis gives 4Q ampere turns per core under normal conditions. Supposing that the microphonemsed will cause the direct current to vary at audible frequencies 1 If such a modulator is placed in the anbetween .1 and-.6 ampere, the direct current magnetization will vary from 10 to ampere turns 'and the e ective resistance as shown on F1 2 will vary between values of approximay 17 ohms and..'l--ohms for a" nor al rad o frequency current'of two amtenna circuit of a tube transmitter, as shown in Fig. 1, the phenomena which occur are rather complex; As themicro hone or magnetization current is varied, o modulator tends to vary its resistance due to change of eddy current lossesybut a variation in the resistance of the antenna circuit causes a drop in the output of the tube since the antenna circuit then no longer fits the plate coupling adjustment necessary to adapt it C. ampere turns its lower :with lower radio frequency currents. On the whole, therefore, the modulator resistance does not vary as much as it would, were the antenna current to remain constant. A net variation in antenna current does, however, occur as the microphone current varies, and by a suitable adjustment of coupling coils 4 and 5, substantially complete modulation of the antenna current can be obtained. Under these conditions the variation of inductance due to the variation of the direct current magnetization is for example, from 1 microhenry to .2 michohenry, which variation is substantially go ii the same order on long as well as short wave lengths although the resistance variation proportionally is smaller for longwave lengths, as it varies directly with th frequency. With short wave lengths (1000 m.) the antenna and loading inductance used will be in the neighborhood of michohenries and the variation of .8

microhenry will be practically ineffective in producing modulation by detuning. From this explanation it will be apparent that the modulation-by the magnetic modulator in accordance with the invention is accom;

plished by varying the resistance without substantial detuning, whereas a ma etic modulator ordinarily acts as a variab e inductance for detuning the antenna.

Having described my invention, what I 1. In radio signaling-with a ferromagnetic modulator and a high frequency generator the method which consists in generating high frequency signaling currents, producing variations in the ma etization of 7 said modulator and modulating said high 7 frequency signaling currents in accordance with the van tions of the iron losses of the modulator w en its magnetization is varied while maintaining the inductance of said ling with a ferromagnetic niodulator ving a' high frequency circuit and a magnetizing winding, the method which consists in supplyln h gh frequency signaling currents to sa1 high frequency circuit, producing variations in the magnetization of said modulator and causing said variations to modulate said signaling currents in accordance with changes in the resistance of the high frequenc circuit produced by changes in the iron osses in the modulator when its magnetization is varied while maintaining the inductance of said modulator substantially constant with respect to the inductance of said high frequency circuit.

3. In radio telephony with a ferromagnetic modulator having a high frequency circuit and a magnetizing winding associated with a microphone, the method which consists in supplying high frequency signaling currents to said high frequency circuit, producing variations in themagnetization of said modulator in accordance with the microphone currents and causing said variations to modulate said signaling currents at speech frequencies in accordance with changes in the resistance of the high frequency winding produced by changes in the eddy current losses in the modulator vwhen its magnetization is varied while maintaining the inductance of said high frequency circuit substantially constant.

4. In radio signaling with a ferromagnetic modulator having a high frequency circuit and a magnetizing winding, the method which consists in producing variations in themagnetization of said modulator, and supplying currents to said high frequency winding at a frequency sufficiently high to cause the amplitude of the high frequency current to be modulated in accordance with the variations of resistance of the high frequency winding due to the iron losses of the modulator while maintaining the inductance of said high frequency circuit substantially constant.

5. In radio signaling with a ferromagnetic modulator having a high frequency winding in a tuned oscillation circuit and a "magnetizing winding, the method which consists in producing variations in the magnetization of said modulator and generatmg currents in said tuned oscillation circuit at a frequency sufiiciently high to cause the. amplitude of the high frequency current to be modulated in accordance with the yariations of resistance of the highfrequency winding due-t0 the iron losses of the modulator while maintaining the tuning of said oscillation circuit substantially constant.

6. In radio signaling with a ferromagnetic modulator having a circuit comprising a high frequency winding connected in an antenna, and a magnetizing winding, the method which consists in producing variations in the magnetization of said modula tor, generating high frequency currents in said circuit and causing said variation of magnetization to change the effective resistance of said winding to a. large extent and to maintain the effective inductance of said winding substantially constant.

7. In a radio transmitting system the combination of an antenna circuit comprising a 'high frequency generator, signaling means,

a battery connected thereto and means for varying the effective resistance of said coil while maintaining the effective inductance thereof relatively, constant for the high frequency currents, said last mentioned means comprising an iron core and a winding, said winding being associated with the signaling means.

9. In a radio telephone transmitting system, the combination of anantenna, a three electrode vacuum tube high frequency generator, a battery, a microphone connected to the battery and means for varying the effective resistance of said antenna and maintaining the effective inductance relatively constant for high frequency currents, said last mentioned means comprising an iron core and a pair of windings, one of said windings being associated with'the antenna and the other winding with the microphone.

JULIUS WEINBERGER. 

